Air Bubbles Introduced from Peripheral Intravenous Lines into the Cerebral Venous System

In the Journal of Neuro-Ophthalmology, Rossiter-Thornton and colleagues (1) illustrate air from a peripheral intravenous line lodged in the superior ophthalmic vein of an 83-year-old woman. We reported a similar case 25 years ago, except that air was trapped in the cavernous sinus (2). Numerous case reports have documented this phenomenon, with air bubbles visible on head CT imaging in 27/12,880 (0.2%) of patients after intravenous line placement (3).

Rossiter-Thornton state that “an air bubble can ascend through the superior vena cava into the dense venous networks of the head and neck if the thorax and head are erect at the time of injection.” They also suggest that atrial fibrillation might have contributed to air embolism by causing venous stasis in the atria.

In fact, once an air bubble reaches the heart, it cannot enter the cerebral venous circulation. It passes via the pulmonary artery into the lungs where it is absorbed. However, if a cardiac wall defect, such as a patent foramen ovale, is present, air can pass from the right heart to the left heart, sometimes causing stroke from arterial air embolism.

In our case, and that described by Rossiter-Thornton, air most likely traveled up the arm, traversed the right subclavian vein and entered the internal jugular vein. There is no reason to postulate that the air ever entered either the right brachiocephalic vein or the superior vena cava. Once in the internal jugular vein, air ascends via the inferior petrosal sinus to reach the cavernous sinus. It remained there in our case, but in Rossiter-Thornton’s case it continued to rise, entering the superior ophthalmic vein. Note that it was arrested at the highest point, just where the superior ophthalmic vein must duck under the superior orbital rim to join the supraorbital vein.

Many clinicians are careless about purging air from syringes and intravenous tubing. Air bubbles can also originate from the dead space in the hub of needles and catheters, as well as the Luer tip of syringes. During surgery, when I point out air bubbles traveling through the intravenous line towards a patient’s arm, I am usually met with a shrug from the anesthetist. Although introduction of small amounts of air rarely causes harm, it is a potential hazard that should be avoided (4). Perhaps a more clever design of the connections between syringes, needles, intravenous tubing, and catheters could alleviate this problem.